<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }
        body {
            background-color: #eee;
        }
        ul {
            width: 140px;
            background-color:crimson;
            list-style: none;
            position: relative;
            left: 60px;
            top: 100px;
            padding: 10px;
        }
        ul li {
           line-height: 30px;
           text-align: center;
           cursor: pointer;
           color: white;
        }
        ul li div {
            color: black;
            display: none;
            /* white-space: nowrap; */
            transition: all .8s;
            width: 400px;
            height: 230px;
            background-color: #ddd;
            position: absolute;
            top: 30px;
            left: 160px;
        }
        ul li:hover {
            background-color: white;
            color: black;
        }
    </style>
</head>
<body>
    <ul>
        <li>家用电器<div>家用电器的二级菜单</div></li>
        <li>手机<div>手机的二级菜单</div></li>
        <li>电脑<div>电脑的二级菜单</div></li>
        <li>男装女装<div>男装女装的二级菜单</div></li>
        <li>生活用品<div>生活用品的二级菜单</div></li>
        <li>汽车<div>汽车的二级菜单</div></li>
        <li>食品<div>食品的二级菜单</div></li>
        <li>彩票<div>彩票的二级菜单</div></li>
    </ul>

    <script src="jquery.js"></script>
    <script>
         $('li').mouseover(function() {
            $(this).children('div').show().parent().siblings('li').children('div').hide()
         })
    </script>
</body>
</html>